Basement membranes are highly specialized extracellular matrices which are strategically positioned between polarized epithelia and the thick collagenous mesenchyme. (Martinez-Hernandez, A., (1984) Lab. Invest., 51: 57-74). In recent years it has been realized that basement membranes act not only as physical scaffolds and molecular filters but also as solid-phase regulators of a variety of cellular processes, including attachment, motility and differentiation (Yurchenco and Schittny, (1990) FASEB J., 4:1577-1590). Basement membranes can also modulate cellular growth by acting as a reservoir for growth factors and by prolonging their in vivo half-life (Saksela, et al., (1988) J. Cell. Biol. 107:743-751; Vigny, et al. (1988) J. Cell. Biol. 131:123-130). The Englebreth-Holm-Swarm (EHS) murine tumor is a transplantable neoplasm; (Swarm, et al., (1963) J. Natl. Cancer Inst. 31:953-974); that has been very useful to the scientific community primarily because of its intrinsic ability to synthesized and deposit large amounts of basement membrane constituents (Orkin, et al., (1977) J. Exp. Med. 145:204-220). Tissue extracts of EHS tumor contain laminin (Timpl, et al. (1979) J. Biol. Chem. 254: 9933-9937), type IV collagen (Kleinman, et al., (1982) Biochemistry 21: 6188-6193), a high-M.sub.r heparin sulfate proteoglycan (Hassell, et al. (1980) Proc. Natl. Acad. Sci. U.S.A. 77: 4494-4498), and entactin/nidogen (Carlin, et al. (1981) J. Biol. Chem. 256: 5209-5214); (Timpl, et al. (1983) Eur. J. Biochem. 137: 455-465), four gene products characteristic of basement membrane matrices (Martinez-Hernandez (1987) Methods Enzymol. 145: 78-103). Although primary cultures of EHS tumor cells have been previously maintained for up to 1 week (Ledbetter, et al. (1985) J. Biol. Chem. 260: 8106-8113), no continuous cell line has been yet established from the EHS tumor. The lack of an EHS-derived cell line has precluded a number of metabolic studies, such as long-term labelling and detailed turnover analysis of various basement membrane macromolecules. Therefore, there is a long-felt need for a phenotypically stable mammalian cell line from the EHS tumor.